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 How-To: Clean Throttle Body, ISC Valve, and IAP Sensor 
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Joined: Fri Aug 31, 2018 5:18 pm
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Location: Fox Valley Wisconsin
scooters and mods: 2 2004 Vinos 2004 Zuma
Post Re: How-To: Clean Throttle Body, ISC Valve, and IAP Sensor
JohnnyFYX wrote:
The Throttle Body Assembly can gum up just as easily as a Carburetor. The main reason why a throttle body assembly gets dirty is because of the emissions required positive crank pressure ventilation hose feedback into the air intake box. The emissions feedback hose connects to the back side of the air intake box, and the other end of this hose connects to the left side of the motor on the nipple of the cam-gear cover. When the motor has excessive or positive crank pressure, the pressure is relieved through the cam gear cover & fed back through the Air Intake Box. This positive pressure also includes oil vapors and in the case of a BBK, you may have oil particulates spray out in greater quantity than in a stock motor. This oil vapor gets sucked into the intake air stream and passed through the Throttle Body Assembly. Usually much of this oil vapor is collected into the transparent oil catch hose that hangs from the bottom of the air intake box; however, the possibility of oil being sucked into the air intake stream still exists.

The end result is a gummed up Throttle Body, ISC (Idle Speed Control) Valve, and IAP (Intake Air Pressure) Sensor. If you don't clean these parts, you can experience a range of issues such as a stuck high or low speed idle RPM, frequent cold motor stalling while at idle, trouble with cold starts in temps below 45F degrees, a damaged idle speed control valve, a clogged intake air pressure sensor/sensor port, a damaged intake air pressure sensor, to verify if the ISC Valve or IAP Sensor has been damaged, you should try cleaning these components as well as the Throttle Body before testing the circuitry as suggested in the factory service manual. Generally you can expect the ECU to notify you with a Check Engine Light if the ISC Valve or IAP Sensor are damaged or defective in one way or another; however, there remains the possibility that the sensor and/or valve are not damaged or defective, but simply dirty (thus not triggering a CEL) and in desperate need of a good cleaning. This How-To will help to illustrate the dis-assembly and cleaning process.

(Note: The Throttle Body shown in this How-To is a 28mm KOSO Throttle Body; the How-To process is identical to the OEM Throttle Body. Also, the motor and parts shown in this How-To have between 15,000 and 30,000 miles on them. The motor has been through a few gasket failures and oil leaks, which is why it's so dirty/grimy. The Throttle Cables shown in this How-To are in need of replacement because the rubber seals on the cables have either cracked or completely failed, causing the internal lubricant to dry out and eventually damage the cables and cause them to rust. These are parts you can inspect, service, clean, replace if necessary while performing this task.)

This image was extracted from the Factory Service Manual in regards to Checking the Throttle Body Assembly... According to the FSM, you shouldn't clean or service the Throttle Body Assembly. IMO, as long as you're careful and don't go overboard with the cleaning fluids, you can successfully clean this part contrary to what the FSM states. IMO, the FSM expects everyone to simply fork over $200+ to replace the Throttle Body Assembly just because it's dirty, and that's completely unacceptable if you can save money by getting your hands a little dirty. Also note that the Green Highlighted section from the FSM instructs you on how to properly Reset the ECU and it's ISC Valve settings... The FSM does not specifically state that this is an ECU Reset; however, this is the standard ECU Reset Procedure. Nowhere else in the FSM does it specify how to Reset the ECU without using the Yamaha FI Diagnostic Tool.
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To start the cleaning process you must first remove the Throttle Body Assembly from the scooter. First remove the Air Intake Box by loosening the intake hose clamp that connects the Air Intake Box to the Throttle Body. Followed by removing the black emissions positive pressure/oil vapor feedback hose from the back of the Air Intake Box, and then removing the two bolts at the bottom of the Air Intake Box that mount it to the top of the CVT housing. The Air Intake Box Assembly can now be removed from the scooter.

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Next, you'll have easy access to the Throttle Body Assembly and it's hose, wire harnesses, and throttle cables. Start by removing the ISC Valve & IAP Sensor wire harness connectors from the Throttle Body... Simply depress the connector's locking tab clip and pull the connector away from the throttle body. Don't pull on the wire harness as this can damage the wires, always remove the wire harness & connector by pulling on the connector itself. After the wire harness connectors have been removed, you can remove the small hose connected to the brass nipple on the Throttle Body. Place the small hose and wire harnesses out of the way and to the side of the Throttle Body.

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On the other side of the Throttle Body, you'll see the Throttle Cables and it's mounting bracket. There are two ways that you can remove the Throttle Cable Bracket, you can either choose to unscrew the Philips Screws that are shown to the left in the above pic, or you can remove the Allen Hex screws shown to the right. I chose to remove the Philips screws because I had more room to work with vs. removing the Allen Hex screws. With the Bracket removed, you'll now have the ability to maneuver the Bracket and Throttle Cables closer to the Black Throttle Linkage (Black Round Disc that the Throttle Cables are connected to). This should give you plenty of slack to remove the Throttle Cables from the Throttle Linkage. Simply unwind the cable from the Throttle Linkage and slide out the Throttle Cable Locking Pin from the Throttle Linkage as shown below.

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Next you'll loosen the hose clamp that attaches the Throttle Body to the Intake Manifold. In the photo shown below, you'll see there are two hose clamps, you only have to loosen the hose clamp that's furthest away from the Throttle Body... It's the hose clamp that clamps the hose down to the Intake Manifold. You do not have to remove the intake manifold, so don't bother wasting your time with it. Once the hose clamp is loose enough, you should be able to pull the Throttle Body Assembly off the Intake Manifold and away from the scooter.

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With the Throttle Body Assembly removed from the scooter, you'll be able to inspect it and clean if necessary. Here are the photos before I cleaned the Throttle Body...

Air Intake Box end of the Throttle Body:
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Intake Manifold end of the Throttle Body:
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Before cleaning the Throttle Body, You must remove the ISC Valve and the IAP Sensor. These components of the Throttle Body Assembly require a Security Torx bit to remove the Tamper Proof Torx Screws. A Security Torx Bit has the standard Torx Star Pattern with a hole in the center of the end of the bit. The Security Torx Bit I used was a T20 to remove the 4 screws that hold the ISC Valve & IAP Sensor to the Throttle Body.

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At this point, whenever you're handling the ISC Valve or the IAP Sensor you should pay close attention to the small parts, o-ring, and gaskets. You should know that these components can only be replaced by purchasing a new $200+/- Throttle Body Assembly as these components are not sold separately.

When you remove the ISC Valve's Tamper Proof Torx Screws and separate the black plastic cover, you'll find that the ISC Valve's Solenoid is also mounted to the Throttle Body by two small Philips Screws. You'll need a Small/Precision Philips Screw Driver to remove these two screws. Be careful not to strip these screws. Also, be aware that the ISC Valve Black Plastic Cover has a rubber gasket that can be easily damaged if you're not careful with it while handling these parts. Once the two small Philips screws are removed, you'll be able to remove the ISC Valve & Solenoid from the Throttle Body. There is a small Spring on the end of the ISC Valve, be careful not to damage or lose this spring when removing the ISC Valve.

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Next you can remove the IAP Sensor by removing the two Tamper Proof Torx screws that mount it to the Throttle Body. Once the two screws are removed, the IAP Sensor can now be gently removed from the Throttle Body. Pay close attention to the small o-ring at the base of the plastic Air Pressure Sensor so that you don't lose this part. Also, there is a small complex gasket that exists on the opposite end of the IAP Sensor. This gasket can be easily torn or lost, so be careful with it as well.

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With the ISC Valve and IAP Sensor removed from the Throttle Body, you can now clean these parts. I suggest that you wear rubber nitrile gloves to keep the cleaner from burning your hands. I sprayed the IAP Sensor directly using the Carburetor/Throttle Body Cleaner and wiped away the excess oil/grime with a cloth/paper towel. Be careful not to damage or lose the gaskets or o-ring in the process. You don't want to soak the sensor in cleaning fluids as this can potentially damage the sensor... simply spray it down to get the majority of the loose oil/dirt/grime off the sensor and then wipe away the rest. It may be useful to clean the smaller crevasses with a q-tip or similar cleaning implement. Once it's wiped clean (doesn't have to be perfect, just clean it as gentle and as best as you can), you can set it aside to air dry for a few minutes. If the crevasses (especially the ones inside the gasket) are not completely dry, go ahead and try to soak up the remaining cleaning fluid with a small piece of paper/cloth towel or a small wad of tissue paper.

Here is the cleaned IAP Sensor: (Note: it's not perfectly clean, but good enough IMO)
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The ISC Valve can be cleaned by directly spraying it with the Carburetor/Throttle Body Cleaner, just avoid spraying the solenoid and it's wires and the black plastic cover. In the photo shown below is the ISC Valve... The part that you'll need to clean is the brass disc (it slides back and forth on a needle thin shaft that is mounted inside the black plastic cone. The Black Plastic Cone is in a fixed position, you should clean both the inside and outside of this Cone by spraying it with carburetor cleaner. Be careful not to spray the circuitry or the back side of the Solenoid (the part that has the wires protruding from it). If you do end up spraying the Solenoid, simply dry it off completely before reinstalling the part. The Solenoid is basically used to move the Brass Disc either closer or further away from the Black Plastic Cone along the needle thin shaft. Spray the Disc and both ends of the shaft it slides on with Carburetor/Throttle Body cleaner. After the ISC Valve is cleaned, allow the part to completely air dry for a few minutes and move on to cleaning the the Throttle Body.

The ISC Valve Spring was also kind of dirty, so I suggest cleaning it as well... Simply spray the spring with the Carburetor/Throttle Body Cleaner and gently wipe away any grime that is still on it.
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Here is the cleaned ISC Valve:
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Next, you'll clean the Throttle Body. For this I recommend using the Carburetor/Throttle Body Cleaner to spray down the inside and outside of the Throttle Body as well as any ports that are used for the ISC Valve and IAP Sensor. A q-tip can be used to get inside the ISC Valve and IAP Sensor ports on the Throttle Body, and then use a cloth or paper towel that is soaked in Carburetor/Throttle Body cleaner to wipe down any areas of the Throttle Body that aren't easily cleaned by just spraying them down. Usually the Throttle Body Butterfly Valve and the areas next to it need wiped down. Thoroughly inspect the entire Throttle Body to see if all areas and crevasses are properly cleaned. Set the Throttle Body aside to air dry for a few minutes.

Here is the cleaned Throttle Body:
Air Intake Box end of the Throttle Body...
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Intake Manifold end of the Throttle Body...
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Cleaned ISC Valve Ports on the Throttle Body...
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Cleaned IAP Sensor Ports on the Throttle Body...
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While the Throttle Body and other components are air drying, you might as well clean up the Intake Manifold. I used a cloth towel and sprayed the towel with Carburetor/Throttle Body cleaner and then proceeded to wiped the inside of Intake Manifold with the cloth towel until it looked visibly clean. I cleaned the inside of the Intake Manifold while it was still mounted to the motor. This part does not need to be removed in order to clean it. Be careful not to spray inside the intake manifold unless you plan to thoroughly clean the intake valves as well. If you do spray Carburetor/Throttle Body Cleaner into the Intake Manifold and thus onto the Intake Valves, then you will have a hard time starting up the scoot on it's first start up after you re-install all the parts. If you do have a hard time starting up the scoot due to excessive cleaner on the intake valves, simply apply WOT or a large amount of Partial Throttle while starting up the scoot. It may take several tries, but eventually it will start up. You should also give it a bit of Throttle to help burn off the excessive cleaner in the combustion chamber.

Here's the cleaned Intake Manifold:
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After a few minutes you can start assembling the components of the Throttle Body in reverse order... Be careful with the ISC Valve Spring and aligning the ISC Valve up with the port on the Throttle Body. Don't force the ISC Valve into the port, simply line it up and it will easily fall into the port with the Black Plastic Cone resting on top of and securing the ISC Valve Spring. Once the ISC Valve is seated into the port, you can thread the two small Philips screws to secure the ISC Valve's Solenoid into its place. Tighten these small screws tight, but don't go overboard to the point of stripping the threads or the head of the screws. Once the Solenoid is mounted, you'll line up the rubber gasket on the Black Plastic ISC Valve Cover to the Throttle Body and mount the Black Plastic Cover with the two Tamper Proof Torx screws. The IAP Sensor, should easily line up with it's port on the Throttle Body, an as long as the small rubber gasket and the small o-ring are in their proper position. Be careful not to mount the IAP Sensor if the gasket and/or o-ring are out of place, as this can damage or destroy these parts. Tighten down the IAP Sensor's Tamper Proof Torx screws (again tighten them down tight, but not too tight to the point where it strips the screws threads or cracks the plastic covers for the valve/sensor.

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Connect the Throttle Body Assembly to the Intake Manifold and tighten down the hose clamp. Re-Connect the Throttle Cables to the Throttle Cable Linkage and mount the Throttle Cable Bracket to the Throttle Body with the two Bracket screws. Connect the small rubber hose to the Throttle Body's Brass Nipple, and then connect the Wire Harnesses to the Throttle Body. The wire harness connectors are uniquely different, so no worries about connecting them in the wrong position. They should Click/Lock into place once they are connected. Install the Air Intake Box by connecting the Intake Hose/Pipe to the Throttle Body and mounting the Air Intake Box to the top of the CVT casing with the two bolts. Tighten down the Air Intake Box's Intake Hose Clamp onto the Throttle Body.

Re-attach the Emissions Crank Pressure Ventilation Hose to the back side of the Air Intake Box. If you'd like to extend the Throttle Body Cleaning service interval, I would highly recommend not re-attaching the Emissions Crank Pressure Ventilation Hose to the back of the Air Intake Box. Instead I would cap the nipple on the back of the Air Intake Box, and attach a Breather Filter to the end of the Emissions Crank Pressure Ventilation Hose. Alternatively, you could attach an oil catch can to the Emissions Crank Pressure Ventilation Hose with an integrated Breather Filter on the Oil Catch Can to let the excessive pressure escape the motor without being fed back into the intake air stream of the motor.

Now that you've completed the process of Cleaning and Re-installing the Throttle Body Assembly, you must perform the ECU Reset Procedure as shown in the first image of this How-To. The instructions can be a tad confusing the way they are written in the FSM, so I will clarify them below...

ECU Reset Procedure:
Start this procedure with the Side Stand in the Up position (you can optionally place the scooter on the center stand). With the Key inserted into the Ignition in the Off position, toggle the Key to the On position for 3 seconds (do not Start the motor), then toggle the Key to the Off position for 3 seconds, followed by the On position for 3 seconds and then Off position for 3 seconds, followed by the On position for 3 seconds and then Off position for 3 seconds. (The On/Off Toggle should be at least 3 times each for On & Off) Next toggle the Key to the On position for 3 seconds and then Start the motor. Let the motor idle for at least 10 minutes prior to giving it any throttle.

:cheers:

_________________
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Athena Sport BBK waiting to go on

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2004 Zuma Malossi sport 70 cc breaking in with stock pipe then Technigas next r polini 107 mm clutch polini green springs polini 2008 zuma torque driver high speed variator 5.7 grams 82 main jet 46 pilot jet needle 1 clip rich stock athena1 4/42 gears 11 to 1 final ratio 50 mph

2005 Eton Beamer (Taiwan Zuma Clone) Airsal sport 70cc 9200 peak rpm top speed 42 77.5 mikuni jet needle 1 clip rich


Mon Dec 24, 2018 12:28 pm
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